Since the NSX is already at the lowest minimum weight possible, if you do this (drop ballast on the rest of the cars), some of the cars like the Lexus and GT-R's will have massive (it's already bad enough) handling/lap time advantages (and considerably better tire wear) over the NSX, particularly on slower speed tracks. Also, being that the Lexus and GT-R already have sizeable advantages on slow speed tracks where draft is of little benefit to the NSX, you must not forget that on high speed tracks (like Monza & La Sarthe) it is quite possible for a top level driver in a GT-R or Lexus to keep pace with a top level driver in a NSX using the slipstream. As the long straights can allow the slower car to keep in touch, particularly deeper into the stints when the NSX's tires tend to fall off sooner. On the other hand, this is COMPLETELY impossible for the NSX driver to achieve on a track like Suzuka, Nurb F, etc. So I think you need to step back and have a better perspective on this 💡
Decreasing the power will do NOTHING to improve the NSX's lap times on slower tracks, particularly in the hands of a skilled driver. If anything, it will just slow it down further. And lets not forget that the Lexus already had a ~ 1 second advantage over the NSX at Laguna (which is relatively short lap @ ~ 1:20). Had you been in the NSX, you would have complained even more than you are now
I haven't driven the Lexus first hand (from what I've heard it's on rails and has great tire wear), but it will likely have a moderate advantage or be on par with ANY of the other cars on just about all but the fastet tracks (Monza and La Sarthe).
I do agree that we don't want to slow the cars down too much or make them all feel lame and handicapped, but the truth is...that's really the only option there is to level the playing field, because if we run the cars at similar weight/hp/aero values there will be HUGE disparities in the performance of the cars...much bigger than what we already have.
The only possible way that I can think of to get the NSX to have similar characterstics as the other other FR cars would be allowing it to run R2's (something that isn't easily policed), while reducing it's hp and taking the ballast off the other cars. Otherwise it's not going to happen, as the NSX is already at it's lowest weight possible